HIGHLY SENSITIVE DETERMINATION OF HYDROGEN-PEROXIDE AND PEROXIDASE WITH TETRATHIAFULVALENE-BASED ELECTRODES AND THE APPLICATION IN IMMUNOSENSING

Redox mediators enable an efficient electron transfer between redox en zymes and the electrochemical surface of amperometric sensors. A stabl e and highly sensitive signal was obtained using a tetrathiafulvalene (TTF)-modified graphite electrode. In the presence of horseradish pero xidase (HRP), hydrogen peroxide (H2O2) was monitored with a detection limit of 7 nM at a potential of +20 mV versus a saturated calomel elec trode (SCE). With a constant concentration of H2O2, the detection limi t for HRP was found to be 150 pM. The accuracy of consecutive measurem ent of HRP in flow-through systems was improved by short-time polarizi ng the TTF-modified graphite electrode at +100 mV versus Ag/AgCl/3 M K CI. Using the TTF-modified graphite electrode in an immune-sandwich ap proach, rabbit-immunoglobulin G was monitored in the range 5-100 ng/ml . (C) 1996 Elsevier Science Limited